The invention relates to a method for aligning a sensor system, and an alignment receiver for implementing the method.
Such sensor systems may be realized in particular in the form of light curtains. Such a light curtain comprises a transmitter unit with an arrangement of light beam emitting transmitters and a receiver unit with an arrangement of light beam receiving receivers. For detection of objects within a monitored area, the transmitter unit and the receiver unit are arranged at opposing edges of the monitored area such that, if the monitored area is empty, the light beams emitted from each transmitter strike its corresponding receiver. An object entering the monitored area is recognized in that at least one of the beam axes formed by the light beams of the light curtain is interrupted.
Before putting the light curtain into operation, i.e. so that is able to detect objects, the transmitter unit and the receiver unit must be suitably aligned. As an aid for such alignment, an alignment laser may for example be used, which emits alignment beams in the visible wavelength range. The alignment laser is mounted retroactively on the transmitter unit or the receiver unit. To align the transmitter unit and the receiver unit, a check is then carried out whether the alignment beams of the alignment laser strike a target on the receiver unit; the target may be provided by a target mark.
The general disadvantage of this procedure is that it is not the beam axes of the light curtain itself, which beam axes are formed by the individual light beams of the transmitter, that are aligned. The alignment beams, as an additional light axis, thus only provide indirect and consequently incomplete information about the actual alignment of the transmitters with the receivers. Such inaccuracies result in particular from tolerances in the mounting position of the alignment laser. Furthermore, the emission characteristics of the alignment laser on the one hand and the transmitter on the other often do not match.
In general, the alignment laser emits alignment beams with a narrow radiation pattern. Nonetheless, and particularly over large distances, the point of impact of the alignment beams on the receiver unit or transmitter unit is poorly visible. In order for the narrow bundle of light to hit the respective target of the receiver unit or the transmitter unit at all, exact positioning of the alignment laser on the transmitter unit or receiver unit is necessary, which makes the adjustment process a laborious one. Finally, it is disadvantageous that, when the unit on which the alignment laser is mounted is itself aligned in order to undertake the adjustment process, the adjusted position is at least partially lost again when the alignment laser is dismounted from the unit.